Membranes used in transmission electron microscopy (TEM) are prepared by a focused ion beam (FIB) that are routinely used to prepare site specific TEM specimens of semiconductor devices. A site is prepared for milling with a focused ion beam and trenches are milled parallel to a 1-2 millimeter thick platinum (Pt) film that has been deposited on the surface. When the film is approximately 300 nanometers thick, the focused ion beam cuts are made to partially detach the section from the wafer. The wafer is tilted to 60.degree., exposing the base and sides of the film. The focused ion beam cuts are then made at the base and sides to produce a "flag on a pole" configuration. The final "release" cuts are usually made at a 0.degree. tilt.
The wafer is usually removed from the focused ion beam and placed under an optical microscope having a long working distance objective lense and a micromanipulator with coarse and fine adjustments. A glass pipette is usually attached to the micromanipulator to remove the TEM film from the wafer. The pipette is usually positioned over the film and lowered to contact it. The electrostatic forces attract the film to the tip of the pipette, which is then raised from the wafer surface. The microscope stage is then moved to bring a TEM grid into view. The pipette with the dangling film is then lowered and the TEM film dropped on the grid.
A major drawback of this process is that once a sample is mounted on the TEM grid, it cannot be further thinned if the membrane is too thick for electron transmission. Thus, a second sample must be prepared, and if the sample is prepared from a specific site on the sample, such as the semiconductor, the specimen is lost. Some uses of an argon mill to further thin the mounted sample have been attempted, but the carbon film typically used on the grid is destroyed and the sample is then lost in the vacuum because it cannot be retained on the grid.